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Given an array of integers numbers that is already sorted in ascending order, find two numbers such that they add up to a specific target number.

Return the indices of the two numbers (1-indexed) as an integer array answer of size 2, where 1 <= answer[0] < answer[1] <= numbers.length.

Example 1:

Input: numbers = [2,7,11,15], target = 9
Output: [1,2]
Explanation: The sum of 2 and 7 is 9. Therefore index1 = 1, index2 = 2.

Solution

• Two pointers

def twoSum(self, numbers: List[int], target: int) -> List[int]:
  
  low, high = 0, len(numbers)-1
  while low < high:
    num = numbers[low] + numbers[high]
    if num == target:
      return (low+1, high+1)
    elif num < target:
      low += 1
    else:
      high -= 1
  return [-1, -1]